Pressure-sensitive or heat-sensitive recording material containing a carbazolyl methane compound

ABSTRACT

The present invention provides a pressure- or heat-sensitive recording material which contains in its color forming system at least one carbazolylmethane compound of the formula ##STR1## wherein Y is an amino-substituted phenyl radical of the formula ##STR2## OR AN INDOLYL RADICAL OF THE FORMULA ##STR3## IN WHICH FORMULAE EACH OF X 1  and X 2  is hydrogen, alkyl of at most 12 carbon atoms which is unsubstituted or substituted, cycloalkyl, phenyl, benzyl, substituted phenyl or substituted benzyl, or X 1  and X 2  together with the nitrogen atom to which they are attached represent a 5- or 6-membered, heterocyclic radical, X 3  is hydrogen, halogen, nitro, lower alkyl or lower alkoxy, each of R 1  and Z 1  is hydrogen, alkyl of not more than 12 carbon atoms which is unsubstituted or substituted; acyl of 1 to 12 carbon atoms, phenyl, benzyl, substituted phenyl or substituted benzyl, and Z 2  is hydrogen, lower alkyl or phenyl, and the rings A, B and D independently can be further substituted. This material yields copies of improved color intensity and lightfastness.

The present invention relates to a pressure-sensitive or heat-sensitiverecording material which contains as colour former in its colour formingsystem at least one carbazolylmethane compound of the general formula##STR4## wherein Y represents an amino-substituted phenyl radical of theformula ##STR5## OR AN INDOLYL RADICAL OF THE FORMULA ##STR6## IN WHICHFORMULAE EACH OF X₁ X₂ independently represents hydrogen, alkyl of atmost 12 carbon atoms which is unsubstituted or substituted by halogen,hydroxyl, cyano or lower alkoxy; cycloalkyl, phenyl, benzyl, or phenylor benzyl which is substituted by halogen, lower alkyl or lower alkoxy,or

X₁ and X₂ together with the nitrogen atom to which they are attachedrepresent a 5- or 6-membered, preferably saturated, heterocyclicradical,

X₃ represents hydrogen, halogen, nitro, lower alkyl or lower alkoxy,each of

R₁ and Z₁ independently represents hydrogen, alkyl of not more than 12carbon atoms which is unsubstituted or substituted by halogen, hydroxyl,cyano or lower alkoxy; acyl of 1 to 12 carbon atoms, phenyl, benzyl, orphenyl or benzyl which is substituted by halogen, lower alkyl, loweralkoxy or nitro, and

Z₂ represents hydrogen, lower alkyl or phenyl, and the rings A, B and Dindependently can be further substituted by cyano, nitro, halogen, loweralkyl, lower alkoxy or lower alkylcarbonyl.

By lower alkyl and lower alkoxy in the definition of the radicals of thecarbazolylmethane compounds are usually meant those groups and groupcomponents which contain from 1 to 5, in particular 1 to 3, carbonatoms. Lower alkyl is for example methyl, ethyl, n-propyl, isopropyl,n-butyl, sec-butyl or amyl, and lower alkoxy is for example methoxy,ethoxy or isopropoxy. Halogen in connection with all the abovesubstituents is for example fluorine, bromine or preferably chlorine.

Alkyl radicals represented by X₁, X₂, R₁ and Z₁ can be straight-chain orbranched. Examples of such alkyl radicals are: methyl, ethyl, n-propyl,isopropyl, n-butyl, sec-butyl, n-hexyl, n-octyl or n-dodecyl.

Substituted alkyl radicals represented by X₁, X₂, R₁ and Z₁ are inparticular cyanoalkyl, haloalkyl, hydroxyalkyl, alkoxyalkyl, eachcontaining 2 to 4 carbon atoms, for example β-cyanoethyl, β-chloroethyl,β-hydroxyethyl, β-methoxyethyl or β-ethoxyethyl.

Cycloalkyl represented by X₁ and X₂ is for example cyclopentyl orpreferably cyclohexyl.

Preferred substituents in the benzyl and phenyl group of the radicals X,Z₁ and R₁ are for example halogen atoms, methyl or methoxy groups.Examples of such araliphatic and aromatic radicals are: p-methylbenzyl,o- or p-chlorobenzyl, o- or p-tolyl, xylyl, o-, m- or p-chlorophenyl oro- or p-methoxyphenyl.

A heterocyclic radical represented by X₁ and X₂ together with thenitrogen atom to which they are attached is for example pyrrolidino,piperidino, pipecolino, morpholino, thiomorpholino or piperazino.

Alkenyl represented by R₁ and Z₁ is for example allyl, 2-methallyl,2-ethallyl, 2-butenyl or octenyl.

An acyl radical within the definition of R₁ and Z₁ is in particularlower alkylcarbonyl, for example formyl, acetyl or propionyl, orbenzoyl. Benzoyl can be substituted in the benzene ring by halogen,methyl or methoxy.

Each of X₁, X₂, Y₂ and Z₁ independently represents preferably loweralkyl or benzyl, whilst Z₂ preferably represents methyl or phenyl.Advantageously, X₁ and X₂ can also represent phenyl or loweralkoxyphenyl. X₃ preferably represents hydrogen, methyl, methoxy orchlorine. R₁ is preferably alkyl of 1 to 8 carbon atoms or benzyl and,in particular, ethyl, n-butyl or n-octyl.

The rings A, B and D are preferably not further substituted, but if theydo contain substituents, each independently is further substituted inparticular by halogen, lower alkyl or lower alkoxy, for example bychlorine, methyl or methoxy. Each benzene ring can advantageouslycontain 1 or 2 substituents. The substituents of the rings A and D arepreferably in the para-position to the nitrogen atom.

Carbazolylmethane compounds which are of practical importance have thegeneral formula ##STR7## wherein Y₁ represents an amino-substitutedphenyl radical of the formula ##STR8## or an indolyl radical of theformula ##STR9## in which formulae each of X₄ and X₅ independentlyrepresents lower alkyl, phenyl, lower alkoxyphenyl or benzyl and X₄ alsorepresents hydrogen, or X₄ and X₅ together with the nitrogen atom towhich they are attached represent pyrrolidino, piperidino or morpholino,

X₆ represents hydrogen, halogen, lower alkyl or lower alkoxy, each of

R₂ and Z₃ independently represents hydrogen, alkyl of not more than 12carbon atoms which is unsubstituted or substituted by halogen, cyano orlower alkoxy; phenyl; or benzyl which is unsubstituted or substituted byhalogen, lower alkyl or lower alkoxy, and

Z₄ represents hydrogen, methyl or phenyl, and each of the rings A₁, B₁and D₁ independently can be further substituted by cyano, halogen, loweralkyl or lower alkoxy.

Preferred carbazolylmethane compounds of the formulae (1) and (2) aboveare those in which the radicals Y are amino-substituted phenyl radicalsof the formula (1a) or (2a).

Particularly interesting carbazolylmethane compounds are those of thegeneral formula (3) or (4) ##STR10## wherein R₃ represents alkyl of 1 to8 carbon atoms, phenyl or benzyl,

W represents hydrogen, halogen, nitro or methyl,

X₇ represents lower alkyl, phenyl, lower alkoxyphenyl or benzyl,

X₈ represents hydrogen, lower alkyl or benzyl,

X₉ represents hydrogen, methyl or methoxy,

Z₄ represents hydrogen, methyl or phenyl, and

Z₅ represents hydrogen, alkyl of 1 to 8 carbon atoms, benzyl or phenyl.

The carbazolylmethane compounds of the formula (3) are preferred.

Particularly preferred compounds of the formula (3) or (4) are those inwhich W is hydrogen. In this case, R₃ in formula (3) preferablyrepresents alkyl of 1 to 8 carbon atoms, in particular lower alkyl, forexample ethyl or n-butyl, X₈ represents lower alkyl, X₇ representsphenyl or lower alkoxyphenyl, and X₉ represents hydrogen or methyl,whilst in formula (4) each of R₃ and Z₄ preferably represents loweralkyl and Z₄ represents methyl.

The carbazolylmethane compounds of the formula (1) are obtained byreacting 1 mole of an aldehyde of the general formula ##STR11## with 2moles of a compound of the general formula (6) or (7) ##STR12## whereinA, B, D, R₁, X₁, X₂,X₃, Z₁ and Z₂ have the given meanings.

The majority of the carbazole aldehydes of the formula (5) are known,for example from J. Am. Chem. Soc. 73, 98-100 (1951). They are obtainedby formylation of the corresponding carbazole compounds withdialkylformamidines in the presence of an acid halide and can also beused direct without isolation for reaction with the compounds of theformula (6) or (7).

The reaction of the compounds of the formula (5) with the compounds ofthe formula (6) or (7) is advantageously carried out at a temperaturebetween 20° and 130° C., preferably between 50° and 115° C. and in thepresence of sulphuric acid, preferably 70 to 98% sulphuric acid. Thereaction time depends on the temperature and is usually from 1 to 8hours. To promote the solubility of the reagents and the product, it ispossible to add lower aliphatic carboxylic acids or alcohols, forexample acetic acid or isopropyl alcohol, to the reaction mixture, inwhich case the reaction temperature is between 20° C. and the refluxtemperature of the mixture. In some cases it is advantageous to add ureain order to shorten the reaction time and to increase the yield. Insteadof sulphuric acid, it is possible to use hydrochloric acid, zincchloride, iron(III) chloride, aluminium chloride, polyphosphoric acid,phosphoroxy chloride, thionyl chloride or phosphorus pentoxide. It isoften advantageous to use acetic anhydride both as reagent and assolvent. In this case, if for example y represents an unsubstitutedindolyl or carbazolyl radical at the nitrogen atom, an acetyl group canbe introduced at the nitrogen atom during the reaction. The reaction canalso be carried out in a water-insoluble solvent using for examplephosphoroxy chloride or catalytic amounts of an organic sulphonic acid,for example p-toluenesulphonic acid.

The isolation of the end product of the formula (1) is effected in amanner which is known per se, for example by pouring the reactionmixture into ice-water, if appropriate while neutralising the acid withan alkaline compound, for example ammonia, an alkali metal hydroxide oran alkali metal carbonate, collecting the precipitate by filtration orevaporating off the water-insoluble solvent, and by washing and dryingthe product, as well as, is appropriate, by chromatography orrecrystallisation of the product, which in certain cases can containinsignificant amounts of polycondensation products.

The carbazolylmethane compounds of the formulae (1) to (4) are normalycolourless or faintly coloured. When these colour formers are broughtinto contact with an acid developer, i.e. an electron acceptor, theyproduce intense orange, red, violet and green shades of excellentlightfastness, depending on the meaning of Y. They are therefore alsovery useful when mixed with other known colour formers, for example3,3-(bis-aminophenyl)-phthalides 3,3-(bis-indolyl)-phthalides,2,6-diaminofluoranes or spiropyranes, in order to give blue, navy blue,grey or black colourations.

The carbazolylmethane compounds of the formula (1) to (4) exhibit bothon clay and on phenolic substrates an improved colour intensity andlightfastness. They are suitable in particular as slowly developingcolour formers for use in a pressure-sensitive recording material, whichcan also be a copying material.

A pressure-sensitive material comprises for example at least one pair ofsheets, which contain at least one colour former of the formulae (1) to(4) dissolved in an organic solvent and an electron acceptor substanceas developer. The colour former effects a coloured marking at thosepoints where it comes into contact with the electron acceptor substance.

Typical examples of such developers are attapulgite clay, silton clay,silica, bentonite, halloysite, aluminium oxide, aluminium sulphate,aluminium phosphate, zinc chloride, kaolin or any clay or organiccompounds with acid reaction, for example unsubstituted orring-substituted phenols, salicylic acid or esters of salicyclic acidand the metal salts thereof, or an acid polymeric material, for examplea phenolic polymer, an alkylphenolacetylene ring, a maleic acid/rosinresin or a partially or completely hydrolysed polymer of maleic acid andstyrene, ethylene, vinyl methyl ether or carboxypolymethylene. Preferreddevelopers are attapulgite clay, silton clay or phenolformaldehyderesin. According to the invention, these developers and, in particular,attapulgite clay and silton clay, can be applied to paper not only inthe customary alkaline to neutral range, for example at pH valuesbetween 7 and 12, preferably between 8 and 10, but also in the acidrange, for example at pH values between 3 and 6.9 preferably between 4and 6, whereby the carbazolylmethane compounds are distinguished in theacid range even by a higher rate and colour intensity during the colourdevelopment. These electron acceptors are preferably applied in the formof a layer to the face of the receiver sheet.

In order to prevent the colour formers contained in thepressure-sensitive recording material from becoming active too soon,they are usually separated from the electron acceptor substance. Thiscan advantageously be accomplished by incorporating the colour formersin foam-like, sponge-like or honeycomb-like structures. Preferably,however, the colour formers are enclosed in microcapsules, which as arule can be ruptured by pressure.

When the capsules are ruptured by pressure, for example with a pencil,and the colour former solution is transferred in this manner to anadjacent sheet which is coated with an electron acceptor, a colouredarea is produced. This colour results from the dye which is formed andwhich is absorbed in the visible range of the electromagnetic spectrum.

The colour formers are encapsulated preferably in the form of solutionsin organic solvents. Examples of suitable solvents are preferablynon-volatile solvents, for example polyhalogenated diphenyl, such astrichlorophenyl or a mixture thereof with liquid paraffin; tricresylphosphate, di-n-butyl phthalate, dioctyl phthalate, tri-chlorobenzene,nitrobenzene, trichloroethyl phosphate, petroleum ether, hydrocarbonoils, such as paraffin, alkylated derivatives of naphthalene ordiphenyl, terphenyls, partially hydrogenated terphenyl, or otherchlorinated or hydrogenated condensed aromatic hydrocarbons.

The capsule walls can be formed evenly around the droplets of the colourformer solution by coacervation, and the encapsulating material canconsist of gelatin and gum arabic, as described e.g. in U.S. Pat. No.2,800,457. The capsules can be formed preferably also from an aminoplastor from modified aminoplasts by polycondensation, as described inBritish Patent Specifications Nos. 989,264, 1,156,725, 1,301,052 and1,355,124.

The microcapsules containing the colour formers of formula (1) can beused for the manufacture of a wide variety of known kinds ofpressure-sensitive copying material. The various systems differsubstantially from one another in the arrangement of the capsules, thecolour reactants and the carrier material.

A preferred arrangement is that in which the encapsulated colour formeris applied as a layer to the back of a transfer sheet and the electronacceptor substance as a layer to the face of a receiving sheet. Howeverthe components can also be used in the paper pulp.

Another arrangement of the constituents consists in the microcapsuleswhich contain the colour former, and the developer, being in or on thesame sheet in the form of one or more individual sheets or being presentin the paper pulp.

Such pressure-sensitive copying materials are described, for example, inU.S. Pat. Nos. 2,730,457, 2,932,582, 3,418,250, 3,418,656, 3,427,180 and3,516,846. Further systems are described in British patentspecifications Nos. 1,042,596, 1,042,597, 1,042,598, 1,042,599 and1,053,935. Microcapsules which contain the colour formers of formula (1)are suitable for each of these systems and for other pressure-sensitivesystems.

The capsules are preferably secured to the carrier by means of asuitable adhesive. Since paper is the preferred carrier material, theseadhesives are principally paper coating agents, for example gum arabic,polyvinyl alcohol, hydroxymethyl cellulose, casein, methyl cellulose ordextrin.

The term "paper" used herein comprises not only normal paper made fromcellulose fibres, but also paper in which the cellulose fibres arereplaced (partially or completely) by synthetic polymer fibres.

The carbazolylmethane compounds of the formulae (1) to (4) can also beused as colour formers in a thermo-reactive recording material. Thisrecording material contains normally at least one carrier, one colourformer one electron acceptor substance and optionally one binder.Thermoreactive recording systems comprise heat sensitive recording andcopying materials and papers. These systems are used, for example, forrecording information, e.g. in electronic computers, teleprinters ortelewriters, and in measuring instruments. The image (mark) formationcan also be effected manually with a heated pen. Laser beams can also beused to produce heat-induced marks. The thermo-reactive recordingmaterial can be so composed that the colour former is dispersed ordissolved in one binder layer and the developer is dissolved ordispersed in the binder in a second layer. A second possibility consistsin dispersing both the colour former and the developer in the binder inone layer. By means of heat the binder is softened at specific areas andthe colour former comes into contact with the electron acceptorsubstance at those points where heat is applied and the desired colourdevelops at once.

The developers are the same electron-accepting substances as are used inpressure-sensitive papers.

Examples of developers are the clays and phenolic resins alredymentioned, or phenolic compounds, for example 4-tert. butylphenol,4-phenylphenol, 4-hydroxydiphenyl oxide, α-naphthol, β-naphthol,4-hydroxymethyl benzoate, 4-hydroxyacetophenone, 2,2'-dihydroxydiphenyl,4,4-isopropylidenediphenol, 4,4'-isopropylidene-bis-(2-methylphenol),4,4'bis-(hydroxyphenyl)valeric acid, hydroquinone, pyrogallol,phloroglucinol, p-, m- and o-hydroxybenzoic acid, gallic acid,1-hydroxy-2-naphthoic acid, as well as boric acid and aliphaticdicarboxylic acids, for example tartaric acid, oxalic acid, maleic acid,citric acid, citraconic acid or succinic acid.

Fusible, film-forming binders are preferably used for the manufacture ofthe thermoreactive recording material. These binders are normallywater-soluble, whereas the colour formers and the developer areinsoluble in water. The binder should be able to disperse and fix thecolour former and the developer at room temperature.

By applying heat the binder softens or melts, so that the colour formercomes in contact with the developer and a colour is able to form.Examples of binders which are soluble or at least swellable in water arehydrophilic polymers, for example polyvinyl alcohol, polyacrylic acid,hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose,polyacrylic amide, polyvinyl pyrrolidone, gelatin and starch.

If the colour former and the developer are in two separate layers, it ispossible to use water-insoluble binders, i.e. binders which are solublein non-polar or only weakly polar solvents, for example natural rubber,synthetic rubber, chlorinated rubber, alkyl resins, polystyrene,styrene/butadiene copolymers, polymethylmethacrylates, ethyl cellulose,nitrocellulose and polyvinyl carbazole. The preferred arrangement,however, is that in which the colour former and the developer arecontained in one layer in a water-soluble binder.

The thermoreactive coatings can contain further additives. To improvethe degree of whiteness, to facilitate the printing of papers, and toprevent the heated pen from sticking, the coatings can contain, forexample, talc, TiO₂, ZnO or CaCO₃ or also organic pigments, for exampleurea/formaldehyde polymers. In order to effect the colour formation onlywithin a limited temperature range, it is possible to add substancessuch as urea, thiourea, acetanilide, phthalic anhydride or otherappropriate fusible products which induce the simultaneous melting ofthe colour former and developer.

In the following Manufacturing Directions and Examples the percentagesare by weight unless otherwise indicated.

MANUFACTURING DIRECTIONS

A. To a solution of 15 ml of glacial acetic acid, 3.8 ml of water and2.9 g of urea are added 10.4 g of N,N-dimethylaniline and 10g ofN-ethylcarbazole aldehyde. The reaction mixture is heated to 60°-70° C.and kept for 5 hours at this temperature. After cooling, the product isprecipitated by the addition of 20 ml of methanol. Recrystallisationfrom acetone/methanol yields 7.1 g of a compound of the formula##STR13## as colourless crystals with a melting point of 160°-161° C. Onsilton clay this colour former slowly develops an intense lightfast bluecolour with λ max. at 610 nm and 515 nm.

B. The procedure of A. is repeated, substituting 11.6 g ofN,N-dimethyl-m-toluidine for N,N-dimethylaniline, affording 15.2 g of acompound of the formula ##STR14## as colourless crystals which melt at268°-271° C. On silton clay this colour former slowly develops anintense lightfast blue colour with λ max. at 610 nm.

C. 6.7 g of N-ethylcarbazole aldehyde and 12.2 g ofN-phenyl-N-methyl-aminobenzene are dissolved in 20 ml of isopropanol andthe solution is warmed to 30° C. To this solution are added dropwise 5.9g of 98% sulphuric acid in such a manner that the temperature does notexceed 35° C. Then 2.7 g of urea are added, the solution is heated to75° C. and stirred for 4 hours at this temperature. After cooling, theacid reaction solution is poured into ice-water and neutralised with 10%sodium hydroxide solution. The precipitate which forms is collected byfiltration and recrystallised from acetone/methanol, affording 7.9 g ofa colourless compound of the formula ##STR15## which melts at 69°-72° C.On silton clay this colour former develops an intense lightfast bluecolour with λ max. at 620 nm.

D. 11.2 g of N-ethylcarbazole aldehyde and 15.9 g of1-ethyl-2-methylindole are dissolved in 10 ml of acetic anhydride. Thesolution is then heated to 110° C. and kept for 4 hours at thistemperature. The solution is then cooled and the product is precipitatedby adding 50 ml of ethanol. The precipitate is collected by filtrationand recrystallised from acetone/methanol, affording 21.3 g of a compoundof the formula ##STR16## as colourless crystals which melt at 151°-154°C. On silton clay this colour former slowly develops an intenselightfast red colour with λ max. at 540 nm.

E. 4.4 g of N-ethylcarbazole aldehyde, 8.5 g ofp-methoxy-N-methyl-diphenylamine and 0.7 g of urea are dissolved in 25ml of sulpholane. To this solution are added dropwise 3.9 g of 98%sulphuric acid in such a manner that the temperature does not exceed 30°C. The reaction mixture is thereafter stirred for 5 hours at 40° C. andthe resultant solution is poured into 150 ml of methanol and neutralisedwith 30% ammonia solution. The precipitate is collected by filtrationand washed with methanol. The crude product is dissolved in methanol andfreed from salt by filtration. The product is precipitated by pouringthe filtrate into methanol, affording 10.4 g of a colourless compound ofthe formula ##STR17## which melts at 87°-89° C. On silton clay thiscolour former slowly develops an intense lightfast blue colour with λmax. at 625 nm.

F. 5 g of N-butylcarbazole aldehyde and 6.5 g of N-phenylpyrrolidine aredissolved in 25 ml of ethylene chloride. To this solution are addeddropwise 6.75 g of phosphoroxy chloride in such a manner that thetemperature does not exceed 40° C. The reaction mixture is subsequentlystirred for 5 hours under nitrogen at 60° C., then poured into water andneutralised with 30% ammonia solution. The ethylene chloride phase isseparated and poured into 200 ml of methanol, whereupon the productprecipitates in crystalline form. The precipitate is collected byfiltration and dried to vacuo at 50° C., affording 3.1 g of a colourlesscompound of the formula ##STR18## which melts at 101°-103° C. On siltonclay this colour former slowly develops an intense lightfast blue colourwith λ max. at 615 nm.

G. 11.1 g of N-ethylcarbazole aldehyde and 23.6 g ofN-benzyl-N-methylaniline are dissolved in 70 ml of ethylene chloride. Tothis solution are added dropwise 18.4 g of phosphoroxy chloride in sucha manner that the temperature does not exceed 40° C. The reactionmixture is then stirred for 6 hours at 70° C. under nitrogen. Thereaction product is then worked up as described in F., affording 18.8 gof a colourless compound of the formula ##STR19## which melts at 82°-85°C. On silton clay this colour former slowly develops an intense lighfastblue colour with λ max. at 610 nm.

H. 8.55 g of N-benzylcarbazole aldehyde and 8.7 g of N,N-dimethylanilineare dissolved in 40 ml of ethylene chloride. To this solution are added11 g of phosphoroxy chloride in such a manner that the temperature doesnot exceed 40° C. The reaction mixture is subsequently stirred for 5hours at 70° C. under nitrogen and the reaction product is worked up asdescribed in F., affording 9.5 g of a colourless compound of the formula##STR20## which melts at 89°-91° C. On silton clay this colour formerslowly develops an intense lightfast blue colour with λ max. at 610 nmand 503 nm.

I. 7.7 g of N-n-octylcarbazole aldehyde and 7.3 g of N,N-dimethylanilineare dissolved in 30 ml of ethylene chloride. To this solution are added9.2 g of phosphoroxy chloride and the mixture is stirred for 4 hours at70° C. under nitrogen. The reaction product is then worked up asdescribed in F., affording 1.6 g of a colourless compound of the formula##STR21## which melts at 85°-88° C. On silton clay this colour formerslowly develops an intense lightfast blue colour with λ max. at 610 nmand 530 nm.n

J. 5 g of N-n-butylcarbazole aldehyde and 7.7 g ofN-methyl-diphenylamine are dissolved in 25 ml of ethylene chloride. Tothis solution are added 6.1 g of phosphoroxy chloride and the mixture isstirred for 6 hours at 70° C. under nitrogen. The reaction product isthen worked up as described in F., affording 7.6 g of a colourlesscompound of the formula ##STR22## which melts at 89°-92° C. On siltonclay this colour former slowly develops an intense lightfast blue colourwith λ max. at 620 nm.

K. 7.7 g of N-n-octylcarbazole aldehyde and 11 g ofN-methyl-diphenylamine are dissolved in 35 ml of ethylene chloride. Tothis solution are added 9.2 g of phosphoroxy chloride and the mixture isstirred for 3 hours at 65°-70° C. under nitrogen. The reaction productis thereafter worked up as described in F., affording 8.2 g of acolourless compound of the formula ##STR23## which melts at 84°-87° C.On silton clay this colour former slowly develops an intense lightfastblue colour with λ max. at 620 nm.

L. 11.1 g of N-ethylcarbazole aldehyde, 15.1 g of3-dimethylamino-anisole and 5 g of urea are suspended in 15 ml ofisopropanol. To this suspension are added 10 ml of 98% sulphuric acid at30°-40° C. The resultant solution is then heated to 75° C. and kept for4 hours at this temperature. After cooling, the solution is poured intoice-water and adjusted to pH 9 with 30% sodium hydroxide solution. Theprecipitate which forms is collected by filtration and washed withwater, methanol and acetone and then dried, affording 17.1 g of acolourless compound of the formula ##STR24## which melts at 234°-237° C.On silton clay this colour former slowly develops an intense lightfastgreyish-blue colour.

M. 6.7 g of N-ethylcarbazole aldehyde and 13.2 g of3-chloro-N,N-diethylaniline are dissolved in 70 ml of ethylene chloride.To this solution are added 11 g of phosphoroxy chloride and the reactionmixture is stirred for 10 hours at 75° C. under nitrogen. The reactionproduct is subsequently worked up as described in F., affording 6.9 g ofa colourless compound of the formula ##STR25## which melts at 112°-115°C. On silton clay this colour former slowly develops an intensegreyish-blue colour.

N. 3.2 g of 6-chloro-N-ethyl-carbazole-3-aldehyde and 2.67 g ofN,N-dimethylaniline are dissolved in 20 ml of ethylene chloride. To thissolution are added 3.4 g of phosphoroxy chloride and the mixture isstirred for 5 hours at 70° C. under nitrogen. The reaction product isthen worked up as described in F., affording 1.7 g of a colourlesscompound of the formula ##STR26## which melts at 118°-121° C. On siltonclay this colour former slowly develops an intense lightfast blue colourwith λ max. at 605 and 515 nm.

O. 44.6 g of N-butylcarbazole are dissolved in 23.2 g of dimethylformamide and 50 ml of ethylene chloride. With stirring, 46 g ofphosphoroxy chloride are added to this solution in such a manner thatthe temperature does not exceed 30° C. The temperature is raised to65°-70° C. in the course of 2 hours and kept thereat for 8 hours. Thereaction mixture is then allowed to cool to 50° C. and 14.4 ml of waterare added, whereupon the temperature rises rapidly to 70° C. Thereaction solution is subsequently stirred for 30 minutes and theintroduction of nitrogen is commenced.. To the solution are added 100 mlof ethylene chloride and 65.9 g of N-methyl-diphenylamine. Afterstirring for 16 hours at 65°-70° C. under nitrogen, the condensation iscomplete. After cooling, the solution is adjusted to pH 7 with 18%aqueous sodium hydroxide solution.

The organic phase is separated, washed with two 200 ml portions of waterand dried over calcined sodium sulphate. To the dry ethylene chloridesolution are added slowly 200 ml of acetone and the mixture is pouredwith stirring into 1500 ml of methanol, whereupon the productprecipitates in white crystalline form. 65°-

The precipitate is collected by filtration and dried in vacuo at 50° C.,affording 94.4 g of the compound of the formula (20). The melting pointand the colour former properties are identical with the particulars ofJ.

EXAMPLE 1 Manufacture of a Pressure-sensitive Copying Paper

A solution of 3 g of the carbazolylmethane compound of formula (13) in97g of partially hydrogenated terphenyl is emulsified in a solution of12 g of pigskin gelatin in 88 g of water of 50° C. A solution of 12 g ofgum arabic in 88 g of 50° C. is then added, followed by the addition of200 ml of water of 50° C. The resultant emulsion is poured into 600 g ofice water and cooled until the temperature is 20° C., in the course ofwhich the coacervation is effected. A sheet of paper is coated with theresultant suspension of microcapsules and dried. A second sheet of paperis coated with with silton clay as follows: 25 g of silton clay aresuspended in 42 g of water and, with vigorous stirring, the pH isadjusted to 10 with 30% sodium hydroxide solution. After addition of 7.5g of a binder, for example latex, the suspension is coated on paper anddried. The first sheet and the sheet of paper coated with silton clayare laid on top of each other with the coated sides face to face.Pressure is exerted on the first sheet by writing by hand or with atypewriter and an intense blue copy of excellent lightfastness slowlydevelops on the sheet coated with silton clay.

If the second sheet is coated with silton clay by adjusting a suspensionof 25 g of silton clay and 42 g of water with 30% sodium hydroxidesolution to a pH of 5, then 7.5 g of a binder are added, and thesuspension is coated on paper, dried, and the procedure is repeated asdescribed above, the colour former of the formula (13) develops itsintense lightfast blue colour markedly more quickly.

EXAMPLE 2 Manufacture of a Thermoreactive Paper

6 g of an aqueous dispersion which contains 1.57% of thecarbazolylmethane compound of the formula (20) and 6.7% of polyvinylalcohol are mixed with 134 g of an aqueous dispersion which contains 14%of 4,4-isopropylidene-diphenol, 8% of attapulgite clay and 6% ofpolyvinyl alcohol. This mixture is applied to a paper and dried.Contacting the paper with a heated ball-point pen produces an intenseblue colour of excellent lightfastness.

Intense and lightfast blue colours can also be obtained on using any ofthe other colour formers of the formulae (11) to (19) and (21) to (24).

I claim:
 1. A pressure-sensitive or heat sensitive recording materialwhich comprises as color formers in its color forming system at leastone carbazolylmethane compound of the formula ##STR27## wherein R₁ isalkyl of 1 to 8 carbon atoms or benzyl, x₁ is phenyl or loweralkoxyphenyl, x₂ is lower alkyl and x₃ is hydrogen or methyl.
 2. Arecording material according to claim 1, wherein R₁ is alkyl of 1 to 8carbon atoms.
 3. A recording material according to claim 1, wherein R₁is alkyl of 1 to 5 carbon atoms.
 4. A recording material according toclaim 1, wherein R₁ is ethyl, n-butyl or n-octyl.
 5. A recordingmaterial to claim 1, wherein R₁ is ethyl, x₁ is phenyl, x₂ is methyl andx₃ is hydrogen.
 6. A recording material according to claim 1, wherein R₁is n-butyl, x₁ is phenyl, x₂ is methyl and x₃ is hydrogen.
 7. Apressure-sensitive recording material according to claim 1 whichcomprises the carbazolylmethane compound dissolved in an organicsolvent, and a solid electron acceptor.
 8. A pressure-sensitiverecording material according to claim 1 in which the carbazolylmethanecompound is encapsulated in microcapsules.
 9. A thermoreactive recordingmaterial according to claim 1 which comprises at least one carrier, thecarbazolylmethane compound, a solid electron acceptor, and optionally abinder.
 10. A process for producing a pressure-sensitive recordingmaterial which contains microcapsules containing a color former and anelectron acceptor, in which the color former is a carbazolylmethanecompound of the formula given in claim 1.